Is it possible

My entire pregnancy so far I have been measuring right on with where I am supposed to be. Well all of a sudden when I went for my 37th week check up I was measuring 5 weeks ahead (meaning 42 weeks). So my question is is it possible that in one week my son could have grown that much to be measuring at 42 weeks? And also I only gained a few oz. when I got weighed so I am thinking that the doctor got it wrong, but I am going for an ultra sound on Monday to confirm what is going on with my lil one.

You may just have extra amniotic fluid this week...